Preheat oven to 350 degrees. In a bowl, sift together flour, baking soda, salt, cinnamon, and nutmeg. In another bowl, mix the sugars, vegetable oil, eggs, Greek yogurt, orange juice, and zucchini. Gradually incorporate the flour mixture into the wet ingredients, being careful not to overmix. Bake in a greased loaf pan for 45 minutes, or until a tester comes out clean.

To make the frosting, beat softened cream cheese, butter, powdered sugar, vanilla extract (lemon extract is also great!). Once the bread has cooled, spread frosting and sprinkle with chopped walnuts.